Intrinsically conductive polymers (ICPs) are known for a wide range of applications including use in printed organic circuits and in organic electronic devices such as organic light emitting diodes (OLEDs), organic photoresponsive devices (in particular organic photovoltaic devices and organic photosensors), organic transistors and memory array devices.
One method of forming ICPs is the Buchwald-Hartwig polymerisation process in which an aryl dihalide monomer is reacted with a monomer containing primary or secondary arylamines in the presence of a palladium catalyst. In the Buchwald-Hartwig polymerisation process a C—N bond is formed between an aromatic carbon atom of an aromatic monomer and a N atom of an arylamine monomer.
US 2004/262574 discloses a method of forming polymers according to the following general process:

In which Ar1, Ar2, Ar3 and Ar4 are aromatic groups, X1 and X2 are halogens, polymer termini B and C represent a hydrogen or halogen atom, m is an integer of at least 1 and n is an integer of at least 2.
US 2004/262574 discloses use of the catalyst dipalladium tri(dibenzylideneacetone) (Pd2(dba)3):

Most polymers exemplified in US 2004/262574 have a weight-average molecular weight of no more than 10,000 Da.
Another method of forming ICPs is Suzuki polymerisation, for example as described in WO 00/53656, WO 03/035796 and U.S. Pat. No. 5,777,070. During Suzuki polymerisation, which takes place in the presence of a palladium catalyst, carbon-carbon bonds form between aromatic carbon atoms of monomers.
WO 00/53656 discloses Suzuki polymerisation in which an aromatic dihalide monomer is polymerised with an aromatic diester monomer. WO 00/53656 discloses formation of poly-(9,9-di(n-octyl)fluorene) according to the following reaction scheme:

It is an object of the invention to provide a method of forming ICPs that enables control of polymer molecular weight over a wide molecular weight range.
J. Am. Chem. Soc., 2007, 129 (23), pp 7236-7237 discloses chain-growth Suzuki polymerisation at room temperature of a fluorene monomer carrying one bromine reactive group and one boronic ester reactive group.
In some applications it may be desirable to provide ICPs with reactive substituents, such as crosslinkable substituents. It is therefore a further object of the invention to provide a polymerization method that can be carried out at a temperature low enough to avoid activation of reactive substituents during polymerisation, such as crosslinking of crosslinking groups.